Forging apparatus and forging method

ABSTRACT

The forging apparatus includes: a fixed punch  21  in which a tapered part  21   a  for molding the diameter enlarged part is formed; a die  30  arranged so as to surround an outer periphery of the fixed punch  21;  and a movable punch  10  that is arranged above the fixed punch  21  so as to be opposed to the fixed punch  21.  The die  30  is floatingly supported and includes a protruding part  33   a  for molding the groove on an inner peripheral surface thereof, and when the movable punch  10  is lowered, an annular blank  40  set between the fixed punch  21  and the die  30  is pressed, and the annular member is molded, the die  30  is lowered along with the movable punch  10,  and the groove is molded on the outer peripheral surface of the diameter enlarged part while molding the diameter enlarged part.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese patent application No. 2018-012653, filed on Jan. 29, 2018, thedisclosure of which is incorporated herein in its entirety by reference.

BACKGROUND

The present disclosure relates to a forging apparatus and a forgingmethod, and particularly relates to a forging apparatus and a forgingmethod for molding an annular member having an outer peripheral surfaceof a diameter enlarged part where grooves are formed, an inner diameterof the diameter enlarged part being gradually enlarged toward one end.

Annular members such as gears having an outer peripheral surface of adiameter enlarged part where teeth and grooves are formed, an innerdiameter of the diameter enlarged part being gradually enlarged towardone end, has been known. These annular members are often molded using aforging apparatus. For example, Japanese Unexamined Patent ApplicationPublication No. 2007-105793 discloses a forging apparatus for molding adiameter enlarged part using a floating die.

SUMMARY

The present inventors have found the following problems regarding theforging apparatus and the forging method for molding the annular memberhaving the outer peripheral surface of the diameter enlarged part wheregrooves are formed, the inner diameter of the diameter enlarged partbeing gradually enlarged toward one end.

In the forging apparatus and the forging method disclosed in JapaneseUnexamined Patent Application Publication No. 2007-105793, after thediameter enlarged part is molded by a forging process, teeth and groovesare formed on the outer peripheral surface of the diameter enlarged partby a machining process. Therefore, there is a problem that yield andproductivity of the annular member to be manufactured are low.

On the other hand, when the teeth and the grooves are concurrentlymolded on the outer peripheral surface of the diameter enlarged partwhile simply molding the diameter enlarged part by the forging process,there is a problem that stress concentrates on an end part of aprotruding part provided at the die for molding the grooves, whichcauses the end part to be worn out, resulting in a significant reductionin the life of the die.

The present disclosure has been made in view of the aforementionedcircumstances and provides a forging apparatus and a forging method withwhich yield and productivity of the annular member to be molded are highand a life of the die is long.

A forging apparatus according to one aspect of the present disclosure isa forging apparatus for molding an annular member having an outerperipheral surface of a diameter enlarged part where a groove is formed,an inner diameter of the diameter enlarged part being gradually enlargedtoward one end, the forging apparatus including:

a fixed punch in which a tapered part for molding the diameter enlargedpart is formed;

a die arranged so as to surround an outer periphery of the fixed punch;and

a movable punch that is arranged above the fixed punch so as to beopposed to the fixed punch, in which

the die is floatingly supported and includes a protruding part formolding the groove on an inner peripheral surface thereof, and

when the movable punch is lowered, an annular blank set between thefixed punch and the die is pressed, and the annular member is molded,the die is lowered along with the movable punch, and the groove ismolded on the outer peripheral surface of the diameter enlarged partwhile molding the diameter enlarged part.

In the forging apparatus according to one aspect of the presentdisclosure, the die includes the protruding part for molding the grooveon the inner peripheral surface thereof, and when the movable punch islowered, the annular blank set between the fixed punch and the die ispressed, and the annular member is molded, the groove is molded on theouter peripheral surface of the diameter enlarged part while molding thediameter enlarged part. Therefore, yield and productivity of the annularmember to be molded are high. Further, since the die is floatinglysupported and is lowered along with the movable punch, the upper end ofthe protruding part is hard to wear out, which prolongs the life of thedie. In this way, with the forging apparatus according to one aspect ofthe present disclosure, the annular member to be molded having highyield and productivity and a die with a long life are achieved.

A recessed part may be provided on a lower surface of the movable punch,and when the movable punch is lowered, an end part of the fixed punchmay be fitted into the recessed part. According to this structure, it ispossible to prevent the blank from entering the gap between the movablepunch and the fixed punch and burrs from occurring.

A forging method according to one aspect of the present disclosure is aforging method for molding an annular member having an outer peripheralsurface of a diameter enlarged part where a groove is formed, an innerdiameter of the diameter enlarged part being gradually enlarged towardone end, the method including:

setting an annular blank between a fixed punch where a tapered part formolding the diameter enlarged part is formed and a die arranged so as tosurround an outer periphery of the fixed punch; and

molding the annular member by lowering a movable punch that is arrangedabove the fixed punch so as to be opposed to the fixed punch andpressing the blank, in which

the die is floatingly supported and includes a protruding part formolding the groove on an inner peripheral surface thereof, and

in molding of the annular member, the die is lowered along with themovable punch, and the groove is molded on the outer peripheral surfaceof the diameter enlarged part while molding the diameter enlarged part.

In the forging method according to one aspect of the present disclosure,the die includes the protruding part for molding the groove on the innerperipheral surface thereof, and when the movable punch is lowered, theannular blank set between the fixed punch and the die is pressed, andthe annular member is molded, the groove is molded on the outerperipheral surface of the diameter enlarged part while molding thediameter enlarged part. Therefore, yield and productivity of the annularmember to be molded are high. Further, since the die is floatinglysupported and is lowered along with the movable punch, the upper end ofthe protruding part is hard to wear out, which prolongs the life of thedie. In this way, with the forging method according to one aspect of thepresent disclosure, the annular member to be molded having high yieldand productivity and a die with a long life are achieved.

A recessed part may be provided on a lower surface of the movable punch,and when the movable punch is lowered, an end part of the fixed punchmay be fitted into the recessed part. According to this structure, it ispossible to prevent the blank from entering the gap between the movablepunch and the fixed punch and burrs from occurring.

According to the present disclosure, it is possible to provide a forgingapparatus and a forging method with which yield and productivity of theannular member to be molded are high and a life of the die is long.

The above and other objects, features and advantages of the presentdisclosure will become more fully understood from the detaileddescription given hereinbelow and the accompanying drawings which aregiven by way of illustration only, and thus are not to be considered aslimiting the present disclosure.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of an annular member molded using a forgingapparatus according to a first embodiment;

FIG. 2 is a cross-sectional view of the annular member molded using theforging apparatus according to the first embodiment;

FIG. 3 is a vertical cross-sectional view of the forging apparatusaccording to the first embodiment;

FIG. 4 is a vertical cross-sectional view of the forging apparatusaccording to the first embodiment;

FIG. 5 is a result of an FEM analysis indicating a plastic flow when aworkpiece 40 is molded using the forging apparatus according to thefirst embodiment;

FIG. 6 is a vertical cross-sectional view of a forging apparatusaccording to a second embodiment;

FIG. 7 is a vertical cross-sectional view of the forging apparatusaccording to the second embodiment; and

FIG. 8 is a result of an FEM analysis indicating a plastic flow when aworkpiece 40 is molded using the forging apparatus according to thesecond embodiment.

DESCRIPTION OF EMBODIMENTS

Hereinafter, with reference to the drawings, specific embodiments towhich the present disclosure is applied will be explained in detail.However, the present disclosure is not limited to the followingembodiments. Further, for the sake of clarity of the description, thefollowing description and the drawings are simplified as appropriate.

First Embodiment Structure of Molded Annular Member

With reference first to FIGS. 1 and 2, an annular member molded using aforging apparatus according to a first embodiment will be explained.

FIG. 1 is a perspective view of the annular member molded using theforging apparatus according to the first embodiment. FIG. 2 is across-sectional view of the annular member molded using the forgingapparatus according to the first embodiment. As shown in FIGS. 1 and 2,an annular member 50 is a metallic gear including a diameter enlargedpart 53 whose inner diameter is gradually enlarged toward one end andteeth 51 and grooves 52 formed on an outer peripheral surface of thediameter enlarged part 53. FIG. 2 shows, besides the annular member 50,a workpiece 40 before molding, that is, a blank. It can also be saidthat the annular member 50 is a workpiece 40 after molding.

As shown in FIG. 2, the diameter enlarged part 53, the teeth 51, and thegrooves 52 in the annular member 50 after molding are not formed in theworkpiece 40 before molding. That is, by forging the workpiece 40, whichis the blank, using the forging apparatus according to the firstembodiment, the diameter enlarged part 53 is molded and the teeth 51 andthe grooves 52 are formed on the outer peripheral surface of thediameter enlarged part 53.

The annular member molded by using the forging apparatus according tothe first embodiment is not limited to a gear and it is sufficient thatthe annular member include a diameter enlarged part whose inner diameteris gradually enlarged toward one end and grooves formed on the outerperipheral surface of the diameter enlarged part.

Structure of Forging Apparatus

With reference next to FIGS. 3 and 4, the forging apparatus according tothe first embodiment will be explained. FIGS. 3 and 4 are verticalcross-sectional views of the forging apparatus according to the firstembodiment.

As a matter of course, the right-handed xyz orthogonal coordinates shownin FIG. 3 and the other drawings are shown just for the sake ofconvenience for explaining the positional relation among components.Typically, the z-axis positive direction is the vertically upwarddirection and the xy-plane forms a horizontal plane, which is commonthroughout the drawings.

As shown in FIGS. 3 and 4, the forging apparatus according to the firstembodiment includes a movable punch (upper punch) 10, a fixed punch(lower punch) 21, and a floating die 30. FIG. 3 shows a state before theworkpiece 40 is forged, which is a state in which the movable punch 10is raised. FIG. 4 shows a state after the workpiece 40 is forged, whichis a state in which the movable punch 10 is lowered. That is, themovable punch 10 can be raised and lowered in the vertical direction(z-axis direction). The workpiece 40 after it is molded shown in FIG. 4is the annular member 50.

As shown in FIGS. 3 and 4, the movable punch 10 is formed of a columnarinner punch 11 and a cylindrical outer punch 12 into which the innerpunch 11 is fitted and inserted. The movable punch 10 is fixed to alower surface of a pressure receiving plate 14 by a punch holder 15,which is an annular plate member. Further, in the examples shown inFIGS. 3 and 4, a disc-shaped spacer 13 is provided between the pressurereceiving plate 14 and the movable punch 10.

More specifically, a recessed part having a circular shape as viewed ina planar view is provided in the central part of the lower surface ofthe pressure receiving plate 14, and a root part of the movable punch 10mates with this recessed part. A flange is provided in the root part ofthe outer punch 12, and the punch holder 15 supports the flange frombelow. Then the punch holder 15 is bolted to the pressure receivingplate 14.

The movable punch 10 may not be divided into the inner punch 11 and theouter punch 12 and they may instead be integrally formed.

As shown in FIGS. 3 and 4, the fixed punch 21 is a columnar die arrangedso as to be opposed to the lower side of the inner punch 11 of themovable punch 10. A tapered part 21 a for molding the diameter enlargedpart 53 of the annular member 50 after molding shown in FIG. 2 is formedon an upper side surface of the fixed punch 21. The fixed punch 21 isplaced on a pressure receiving plate 22 a. A pressure receiving plate 22b into which the fixed punch 21 is fitted and inserted is placed on thepressure receiving plate 22 a, and the fixed punch 21 is fixed to thepressure receiving plate 22 a. Further, a pressure receiving plate 22 cis placed on the pressure receiving plate 22 b.

More specifically, a cutout part is provided on an upper surfaceperiphery of the pressure receiving plate 22 a. Further, a protrusion isprovided on a lower surface periphery of the pressure receiving plate 22b. The pressure receiving plate 22 b is placed on the pressure receivingplate 22 a in such a way that the cutout part of the pressure receivingplate 22 a mates with the protrusion of the pressure receiving plate 22b. In a similar way, a cutout part is provided on an upper surfaceperiphery of the pressure receiving plate 22 b. Further, a protrusion isprovided on a lower surface periphery of the pressure receiving plate 22c. The pressure receiving plate 22 c is placed on the pressure receivingplate 22 b in such a way that the cutout part of the pressure receivingplate 22 b mates with the protrusion of the pressure receiving plate 22c.

As shown in FIGS. 3 and 4, the pressure receiving plates 22 a and 22 b,and 22 c are accommodated in a pressure receiving plate holder 23. Thepressure receiving plate holder 23 is formed of cylindrical body parts23 a and 23 b, and a lid part 23 c, which is an annular plate member.More specifically, the pressure receiving plates 22 a and 22 b areaccommodated in the cylindrical body part 23 a. The pressure receivingplate 22 c is accommodated in the cylindrical body part 23 b placed onthe body part 23 a. Further, the floating die 30 is also accommodated inthe body part 23 b. The lid part 23 c is placed on the body part 23 band is fixed thereto.

As shown in FIGS. 3 and 4, a knockout ring 24, which is a cylindricaldie into which the fixed punch 21 is fitted and inserted, is placed onthe pressure receiving plate 22 b while the workpiece 40 is beingmolded. The knockout ring 24 is pushed upwardly (in the z-axis positivedirection) by a knockout pin 25 that penetrates through the pressurereceiving plates 22 a and 22 b. After the workpiece 40 is molded, theknockout ring 24 is pushed upwardly, whereby the molded workpiece 40 canbe taken out from the floating die 30.

As shown in FIGS. 3 and 4, the floating die 30, which is an annular die,is formed of a case 31 and insert dies 32 and 33. The floating die 30 isfloatingly supported by a back-pressure pin 34 that penetrates throughthe pressure receiving plates 22 a and 22 b, and 22 c. The insert dies32 and 33, both of which have the annular shape, are fit into theannular case 31 by shrink fitting or the like. The insert die 32arranged on the upper side of the annular case 31 and the insert die 33arranged on the lower side thereof contact each other. The insert dies32 and 33 may be integrally formed. Further, the case 31 and the insertdies 32 and 33 may be integrally formed.

A protruding part 33 a is formed on an inner peripheral surface of theinsert die 33. By this protruding part 33 a, the grooves 52 can bemolded on the outer peripheral surface of the annular member 50 shown inFIG. 1. Further, a recessed part that corresponds to the protruding part33 a of the insert die 33 is provided on an outer peripheral surface ofthe knockout ring 24, whereby the knockout ring 24 can be fitted andinserted into the insert die 33.

Operation of Forging Apparatus

Next, with reference to FIGS. 3 and 4, an operation of the forgingapparatus according to the first embodiment, that is, a forging method,will be explained.

As shown in FIG. 3, in the state in which the movable punch 10 israised, the annular workpiece 40, that is, the blank, is set between thefixed punch 21 and the floating die 30.

Next, as shown in FIG. 4, the movable punch 10 is lowered and theworkpiece 40 is pressed, whereby the annular member 50 shown in FIG. 1is molded. In this case, the inner punch 11 is inserted into thethrough-hole of the annular workpiece 40. Therefore, the upper innerperipheral surface of the workpiece 40 (i.e., the annular member 50) ismolded by the lower outer peripheral surface of the inner punch 11. Onthe other hand, the outer punch 12 presses the upper surface of theworkpiece 40. Therefore, the upper end surface of the workpiece 40(i.e., the annular member 50) is molded by the lower surface of theouter punch 12. Further, the lower inner peripheral surface of theworkpiece 40 (i.e., the annular member 50) is molded by the upper outerperipheral surface of the fixed punch 21.

Now, as shown in FIG. 4, a cutout part is provided on a lower surfaceperiphery of the outer punch 12. When the movable punch 10 is lowered,this cutout part of the outer punch 12 mates with the floating die 30and then the floating die 30 is lowered along with the movable punch 10.FIG. 4 shows a stroke S of the floating die 30. The outer peripheralsurface of the workpiece 40 (i.e., the annular member 50) is molded bythe inner peripheral surface of the floating die 30. At this timing, asdescribed above, the grooves 52 of the annular member 50 shown in FIG. 1are molded on the outer peripheral surface of the workpiece 40 by theprotruding part 33 a formed on the inner peripheral surface of theinsert die 33 of the floating die 30. On the other hand, the lower endsurface of the workpiece 40 (i.e., the annular member 50) is molded byan upper end surface of the knockout ring 24.

Now, a result of a Finite Element Method (FEM) analysis of a plasticflow in the case in which the workpiece 40 is molded using the forgingapparatus according to the first embodiment will be explained. FIG. 5 isa result of the FEM analysis showing the plastic flow in the case inwhich the workpiece 40 is molded using the forging apparatus accordingto the first embodiment. FIG. 5 shows cross-sectional shapes of theworkpiece 40 when the molding is started, during the molding, and whenthe molding is completed. The three diagrams shown in FIG. 5 correspondto an enlarged view of an area V surrounded by the dashed line in FIG.4.

As shown by the outline arrows in FIG. 5, when the movable punch 10 (theinner punch 11 and the outer punch 12) is lowered and the workpiece 40is pressed, the workpiece 40 is pushed toward the knockout ring 24between the fixed punch 21 and the insert dies 32 and 33 of the floatingdie 30. In this case, the diameter of the workpiece 40 is enlarged bythe tapered part 21 a of the fixed punch 21. Therefore, as shown by theblack arrows in FIG. 5, the workpiece 40 is subjected to plastic flow inthe x-axis positive direction, that is, toward the insert die 33.Therefore, the grooves 52 of the annular member 50 shown in FIG. 1 aremolded on the outer peripheral surface of the workpiece 40 by theprotruding part 33 a formed on the inner peripheral surface of theinsert die 33. The tooth 51 is molded between the grooves 52.

As described above, by using the forging apparatus according to thefirst embodiment, the grooves 52 can be molded on the outer peripheralsurface of the diameter enlarged part 53 while molding the diameterenlarged part 53 (see FIG. 2) of the annular member 50 shown in FIG. 1.Therefore, with the forging apparatus according to the first embodiment,the annular member 50 to be molded having high yield and productivity isachieved.

Further, the insert die 33 is floatingly supported and is lowered alongwith the movable punch 10, that is, the workpiece 40. Therefore, it ishard for the upper end of the protruding part 33 a of the insert die 33to wear out, which prolongs the life of the insert die 33.

Accordingly, with the forging apparatus according to the firstembodiment, the annular member to be molded having high yield andproductivity and a die with a long life are achieved.

Second Embodiment

With reference next to FIGS. 6 and 7, a structure and an operation of aforging apparatus according to a second embodiment will be explained.FIGS. 6 and 7 are vertical cross-sectional views of the forgingapparatus according to the second embodiment.

As shown in FIG. 5, in the forging apparatus according to the firstembodiment, when the molding is completed, the workpiece 40 may enterthe gap between the inner punch 11 of the movable punch 10 and the fixedpunch 21 and a burr 40 a may occur.

On the other hand, as shown in FIGS. 6 and 7, in the forging apparatusaccording to the second embodiment, a recessed part 11 a having acircular shape as viewed in a plane view into which the end part of thefixed punch 21 is fitted is provided on the lower surface of the innerpunch 11 of the movable punch 10. Further, the height of the end part ofthe fixed punch 21 of the forging apparatus according to the secondembodiment is larger than the height of the end part of the fixed punch21 of the forging apparatus according to the first embodiment by thedepth of the recessed part 11 a.

As shown in FIG. 7, when the movable punch 10 is lowered, the end partof the fixed punch 21 is fit into the recessed part 11 a of the innerpunch 11.

Now, a result of an FEM analysis of a plastic flow in a case in whichthe workpiece 40 is molded using the forging apparatus according to thesecond embodiment will be explained. FIG. 8 is a result of the FEManalysis showing the plastic flow when the workpiece 40 is molded usingthe forging apparatus according to the second embodiment. FIG. 8 showscross-sectional shapes of the workpiece 40 when the molding is started,during the molding, and the molding is completed. The three diagramsshown in FIG. 8 correspond to an enlarged view of an area VIIIsurrounded by the dashed line in FIG. 7.

As shown by the outline arrows in FIG. 8, when the movable punch 10 (theinner punch 11 and the outer punch 12) is lowered and the workpiece 40is pressed, the workpiece 40 is pushed toward the knockout ring 24. Inthis case, the diameter of the workpiece 40 is enlarged by the taperedpart 21 a of the fixed punch 21. Therefore, as shown by the blackarrows, the workpiece 40 is subjected to plastic flow in the x-axispositive direction, that is, toward the insert die 33. Therefore, thegrooves 52 of the annular member 50 shown in FIG. 1 are molded on theouter peripheral surface of the workpiece 40 by the protruding part 33 aformed on the inner peripheral surface of the insert die 33. The tooth51 is molded between the grooves 52.

As described above, by using the forging apparatus according to thesecond embodiment, the grooves 52 can be molded on the outer peripheralsurface of the diameter enlarged part 53 while molding the diameterenlarged part 53 (see FIG. 2) of the annular member 50 shown in FIG. 1.Therefore, with the forging apparatus according to the secondembodiment, the annular member 50 to be molded having high yield andproductivity is achieved, like in the forging apparatus according to thefirst embodiment.

Further, the insert die 33 is floatingly supported, and is lowered alongwith the movable punch 10, that is, the workpiece 40. Therefore, theupper end of the protruding part 33 a of the insert die 33 is hard towear out, which prolongs the life of the insert die 33. That is, withthe forging apparatus according to the second embodiment, a die with along life is achieved, like in the forging apparatus according to thefirst embodiment.

Therefore, with the forging apparatus according to the second embodimentas well, the annular member to be molded having high yield andproductivity and a die with a long life are achieved.

Further, in the forging apparatus according to the second embodiment,when the movable punch 10 is lowered, the end part of the fixed punch 21is fitted into the recessed part 11 a of the inner punch 11. Therefore,when the molding is completed, a gap is not generated between the innerpunch 11 of the movable punch 10 and the fixed punch 21. It is thereforepossible to prevent the workpiece 40 from entering the gap between theinner punch 11 and the fixed punch 21 and the burr 40 a (see FIG. 5)from occurring.

Since the other structures and the operations are similar to those ofthe forging apparatus according to the first embodiment, thedescriptions thereof will be omitted.

From the disclosure thus described, it will be obvious that theembodiments of the disclosure may be varied in many ways. Suchvariations are not to be regarded as a departure from the spirit andscope of the disclosure, and all such modifications as would be obviousto one skilled in the art are intended for inclusion within the scope ofthe following claims.

What is claimed is:
 1. A forging apparatus for molding an annular member having an outer peripheral surface of a diameter enlarged part where a groove is formed, an inner diameter of the diameter enlarged part being gradually enlarged toward one end, the forging apparatus comprising: a fixed punch in which a tapered part for molding the diameter enlarged part is formed; a die arranged so as to surround an outer periphery of the fixed punch; and a movable punch that is arranged above the fixed punch so as to be opposed to the fixed punch, wherein the die is floatingly supported and includes a protruding part for molding the groove on an inner peripheral surface thereof, and when the movable punch is lowered, an annular blank set between the fixed punch and the die is pressed, and the annular member is molded, the die is lowered along with the movable punch, and the groove is molded on the outer peripheral surface of the diameter enlarged part while molding the diameter enlarged part.
 2. The forging apparatus according to claim 1, wherein a recessed part is provided on a lower surface of the movable punch, and when the movable punch is lowered, an end part of the fixed punch is fitted into the recessed part.
 3. A forging method for molding an annular member having an outer peripheral surface of a diameter enlarged part where a groove is formed, an inner diameter of the diameter enlarged part being gradually enlarged toward one end, the method comprising: setting an annular blank between a fixed punch where a tapered part for molding the diameter enlarged part is formed and a die arranged so as to surround an outer periphery of the fixed punch; and molding the annular member by lowering a movable punch that is arranged above the fixed punch so as to be opposed to the fixed punch and pressing the blank, wherein the die is floatingly supported and includes a protruding part for molding the groove on an inner peripheral surface thereof, and in molding of the annular member, the die is lowered along with the movable punch, and the groove is molded on the outer peripheral surface of the diameter enlarged part while molding the diameter enlarged part.
 4. The forging method according to claim 3, wherein a recessed part is provided on a lower surface of the movable punch, and when the movable punch is lowered, an end part of the fixed punch is fitted into the recessed part. 